Interview on Time Friend

Frontend Interview Knowledge Collection - JavaScript

Mon, 07 Jan 2019 22:17:36 +0000

JavaScript Interview Knowledge Summary

1. Introduce the basic data types of JS.

JS has six basic data types: Undefined, Null, Boolean, Number, String, and the Symbol type added in ES6,
which represents a unique and immutable data type after creation. Its appearance is mainly to solve the problem of possible global variable conflicts.

2. How many types of values does JavaScript have? Can you draw their memory diagram?

Related knowledge points:

Frontend Interview Knowledge Collection - HTML

Sun, 06 Jan 2019 22:17:36 +0000

HTML Interview Knowledge Summary

1. What is the purpose of DOCTYPE?

Related knowledge points:

IE5.5 introduced the concept of document mode, which is implemented through document type (DOCTYPE) switching.

The <!DOCTYPE> declaration is located at the first line of an HTML document, before the <html> tag. It tells the browser's parser which document standard to use for parsing.

The absence or incorrect format of DOCTYPE will cause the document to render in compatibility mode.

Answer (refer to 1-5):

Frontend Interview Knowledge Collection - CSS

Sat, 05 Jan 2019 22:17:36 +0000

CSS Interview Knowledge Summary

1. Introduce the standard CSS box model? How is the low-version IE box model different?

Related knowledge points:

(1) There are two box models: IE box model (border-box) and W3C standard box model (content-box)
(2) The box model consists of four parts: content, padding, margin, border

Difference between IE box model and W3C standard box model:

(1) W3C standard box model: width and height properties only include content, not border and padding
(2) IE box model: width and height properties include content, border, and padding, referring to content
+padding+border.

In IE8+ browsers, which box model to use can be controlled by box-sizing (a new CSS property). The default value is content-box, which is the standard box model.
If box-sizing is set to border-box, the IE box model is used. In IE6, 7, 8, if DOCTYPE is missing, the box model will be interpreted as IE box model.
If DOCTYPE is declared in the page, all browsers will interpret the box model as the W3C box model.

Answer:

Frontend Interview Knowledge Collection - Comprehensive

Fri, 04 Jan 2019 22:17:36 +0000

HTML, HTTP, Web Comprehensive Questions

Common sorting algorithm time complexity and space complexity

What SEO should frontend pay attention to

Reasonable title, description, keywords: search engines weight these three in descending order. Title should emphasize key points, with important keywords appearing no more than twice and positioned early. Different pages should have different titles. Description should summarize page content concisely, with appropriate length and no keyword stuffing. Different pages should have different descriptions. Keywords should list important keywords only.
Semantic HTML code compliant with W3C standards: semantic code helps search engines understand web pages easily.
Important content HTML code placed first: search engines crawl HTML from top to bottom. Some search engines have length limits on crawling, so placing important content first ensures it gets crawled.
Don’t output important content with JS: crawlers don’t execute JS to get content.
Minimize iframe usage: search engines don’t crawl content inside iframes.
Non-decorative images must include alt attributes.
Improve website speed: website speed is an important factor in search engine ranking.

Session tracking methods in web development

cookie
session
URL rewriting
Hidden input
IP address

Difference between `<img>`’s title and alt

title is one of the global attributes, used to provide additional advisory information for elements. It’s usually displayed when the mouse hovers over the element.
alt is a unique attribute of <img>, an equivalent description of the image content. It’s displayed when the image cannot load and is used by screen readers to interpret images. It improves image accessibility. Except for purely decorative images, it must have meaningful values, and search engines focus on analyzing it.

What is doctype? Examples of common doctypes and their characteristics

<!doctype> declaration must be at the top of the HTML document, before the <html> tag. In HTML5, it’s case-insensitive.
<!doctype> is not an HTML tag; it’s an instruction to tell the browser which HTML version the current page uses.
Modern browser HTML layout engines determine whether to use quirks mode or standards mode for rendering by checking the doctype. Some browsers have a “almost standards” mode.
In HTML4.01, <!doctype> points to a DTD. Since HTML4.01 is based on SGML, the DTD specifies markup rules to ensure the browser renders content correctly.
HTML5 is not based on SGML, so DTD is not needed.

Common doctypes:

Interview on Time Friend

Frontend Interview Knowledge Collection - JavaScript

JavaScript Interview Knowledge Summary

1. Introduce the basic data types of JS.

2. How many types of values does JavaScript have? Can you draw their memory diagram?

Frontend Interview Knowledge Collection - HTML

HTML Interview Knowledge Summary

1. What is the purpose of DOCTYPE?

Frontend Interview Knowledge Collection - CSS

CSS Interview Knowledge Summary

1. Introduce the standard CSS box model? How is the low-version IE box model different?

Frontend Interview Knowledge Collection - Comprehensive

HTML, HTTP, Web Comprehensive Questions

Common sorting algorithm time complexity and space complexity

What SEO should frontend pay attention to

Session tracking methods in web development

Difference between <img>’s title and alt

What is doctype? Examples of common doctypes and their characteristics

Difference between `<img>`’s title and alt